Our work with
Near-Field Scanning Optical Microscopy led us to use
pulled (tapered) fiber optic probes as intracellular
sensors. The tips of these fibers were either coated
with a layer of plasticized PVC

Artist's rendition of an optode inserted into a red
blood cell

containing sensor materials, or they had
a small bit of sensor material on the end which was
photo-polymerized. These fiber-based optical nanosensors,
called Optodes (as opposed to traditional, larger
Electrodes) can be inserted into single cells to sense
analyte levels. This technique works well, but even
though the tip of the sensor may only be 100 nm in
diameter, the fiber body quickly becomes larger up the
taper and can create problems. Only two, or maybe three,
sensors can be inserted at once into a large cell. The
insertion can also damage the cell to the point that the
cell's response may not be representative of its natural
state.